NADH Oxidation Using Carbonaceous Electrodes Modified with Dibenzo‐Dithia‐Diazapentacene

Abstract

The electrochemical and the electrocatalytic behavior for NADH oxidation of a newly synthesized phenothiazine derivative, 16H,18H-dibenzo[c,1]-7,9-dithia-16,18-diazapentacene (DDDP), adsorbed on solid spectrographic graphite and on graphite powder or on zirconium phosphate (ZP), both entrapped in carbon paste, were compared. Experiments using cyclic voltammetry and a rotating disk electrode, performed in different experimental conditions (various pH values and NADH concentrations), showed that i) in the pH range between 4 and 8, the E8× value for DDDP adsorbed on ZP becomes pH independent; ii) in contrast to other redox mediators, adsorption of DDDP on ZP induced a significant negative shift of the E8× value; iii) the reaction rate for electrocatalytic oxidation of NADH is markedly increased by adsorbing the mediator on ZP, being further improved by the presence of Ca 2 ions in the solution.

Electrochemical behavior of carbon paste electrodes modified with methylene green immobilized on two different X type zeolites

“…This result is similar to those obtained for (i) MG [17] and other redox mediators [22,23] adsorbed on zirconium phosphate, for NADH electrocatalytic oxidation and (ii) methylene blue immobilized on a mordenite type zeolite for ascorbic acid mediated electrooxidation [9]. As suggested [9], the mediator entrapment into the channels of zeolite in a confined position, where the acidity of the environment surrounding the dye does not change with the solution pH, could be a reasonable cause for the independence of E 0 ¢ towards pH variation.…”

“…On the other hand, the k s values, as well as the transfer coefficient (a), slightly decrease with increase in supporting electrolyte pH. In comparison with other k s values published for modified electrodes based on phenothiazine derivatives mediators [22,23,26] the values reported here are of the same order of magnitude.…”

Influence of the Electrode Material on the Electrochemical Behavior of Carbon Paste Electrodes Modified with Meldola Blue and Methylene Green Adsorbed on a Synthetic Zeolite

“…2). This behavior was similar to that noticed for CPEs modified with MG adsorbed on the same zeolite, but when using graphite powder as electrode material [3] and also similar to those obtained for MG [5,8] and other redox mediators [5,9,29] adsorbed on zirconium phosphate. However, for pH values higher than 7, both mediators showed a E8' vs. pH dependence expected for a redox process involving 2 e À /1 H þ (ca.…”

Synthesis and Electrochemical Characterization of Poly(2‐methoxy‐4‐vinylphenol) with MWCNTs

“…The obtained value for the rate constant for the catalytic reaction is close to those obtained from chronoamperometric studies. Also, the value of k obs is higher when compared with previously reported data [14,[17][18][19].…”